Photodynamic therapy, PDT, has now reached the level of being an accepted treatment for a number of situations, among which are acne, wrinkles or even several forms of cancer.
Irradiating skin with light stemming from LEDs for treating skin disorders is known, for example to treat acne. The document US 2011/0224598 describes a method of treating inflammatory acne on the skin of a patient, the method comprising irradiating the skin of the patient with radiant infrared light emitting diode (LED) light, subsequently applying the photosensitizing agent 5-aminolevulinic acid (ALA) onto the skin of the patient and irradiating the ALA treated skin with visible LED light. The method described demands high constraint from a patient, as s/he has to undergo an initial 15-minute exposure to light, followed by a 60-minute application of ALA and then a final light exposure of 23 minutes. Such sessions have to be repeated regularly for the therapy to become effective.
It is known that by irradiating skin by emitting light as invisible light in the range of 800 nm to 1100 nm can be used to heal skin diseases. For example, it is known that irradiating the skin with a wavelength of around 835 nm is used for wound healing and around 1070 nm for cold sore surface treatment.
In general, by emitting light of a certain wavelength, for example from 400 to 700 nm, treatment of a skin condition can be performed. LEDs can trigger natural intracellular photo-biochemical reactions. To have any effect on a living biological system, LED-emitted photons must be absorbed by a molecular chromophore or photoacceptor. Light, at appropriate doses and wavelengths, is absorbed by chromophores and other light-absorbing entities within the mitochondria and cell membranes of cells. For example, it is known that by irradiating the skin with a wavelength of around 630 to 660 nm, a stimulation of cell metabolism is caused that activates the generation of collagen in the skin allowing to regenerate the skin, such as reducing wrinkles It is known that a threshold level of power of irradiation must be achieved before such natural process can happen and that the irradiation must take place for a certain duration.
Thus, the time and power of irradiation is important to generate collagen.
Furthermore, the irradiation heats the skin. It is known that too much heat, this uncontrollable level of temperature can have undesirable photo-biochemical reactions or may incur damage to the skin, so that such should be avoided. There are several ways described to limit such heating of the skin.
The document DE 3134953 describes an infrared irradiation device that comprises an infrared light source that is designed as an infrared laser and whose light is directed at the area of skin to be treated medically/therapeutically. The infrared laser is controlled by a control circuit and emits coherent infrared pulse signals at a frequency of 0.1 Hz to 5 kHz, preferably 8 to 50 Hz. The frequency can be adjusted by means of an adjustment member as a function of the skin temperature, that can be measured by means of a temperature sensor and can be displayed in an optical display arrangement. The output of the infrared laser is low, so that the irradiated area of skin is not appreciably heated. According to this document, the skin should not heat to more than 42° C. to avoid damage.
The document WO 91/18646 discloses a device and method for photothermotherapy effected by pulsed ultraviolet, visible or infrared laser radiation passing through a system that assures the necessary laser pulse fluence to a bio-tissue treatment region. While the pulsed local heating of micro regions in the tissue reaches therapeutic levels a unit measuring the local heating by a single pulse and the average heating by a train of pulses controls, by way of feedback, a control unit that determines the pulse energy and repetition period and the total exposure dose to provide a required therapeutic effect without risk of thermal damage to the exposed tissue region.
The document U.S. Pat. No. 6,238,424 discloses an apparatus for external medical treatment with light. A light-emitting device is provided that is adapted to be held in close proximity to the body of an individual and that includes light-emitting diodes or corresponding elements that are adapted to emit monochromatic light of a first wavelength. The light emitting device is driven by a drive arrangement for causing the light-emitting device to emit the monochromatic light over a first predetermined time period in a first state, and thereafter emit selectively monochromatic light of a different wavelength than the first wavelength and over a second predetermined time period in a possible second state. The drive arrangement causes the light-emitting device to pulsate the emitted light in accordance with a predetermined pulse frequency or series of pulse frequencies over the respective time periods, and causes the light-emitting device to emit the pulsating light with a pulse length that lies within an interval of about 60% to about 90% of the time between respective start edges of two mutually sequential pulses.
The document EP 1140288 discloses an apparatus for external medical treatment administered with the aid of light. The apparatus includes a light-emitting device that is intended to be held against or in the close proximity of the patient's body, and means for driving the light-emitting device, wherein the light-emitting device includes light-emitting diodes or corresponding elements adapted to emit monochromatic light, wherein the drive means is adapted to cause the light-emitting device to emit one or more types of monochromatic light over one or more predetermined time periods and to pulsate the light emitted in accordance with a predetermined pulse frequency or series of pulse frequencies over said time periods, wherein said drive means includes a computer and circuits for driving the light-emitting diodes, wherein the computer includes input means for inputting data relating to an intended treatment, wherein the computer is adapted to deliver electric signals to the drive circuits, wherewith intended light-emitting diodes function to emit light within predetermined time periods and at predetermined pulse repetition frequencies. The invention is characterised in that at least the drive circuits of the drive means are mounted in the light-emitting device.
Although such devices may avoid overheating of the skin, they are complicated and often require a separate computer for controlling the operation thereof. Moreover, some of said devices require a skin temperature sensor.
The present invention addresses these problems in a handheld and battery-operated light pen dispenser as defined in the appended claims.